Phase shift mask and phase shift mask blank

ABSTRACT

A phase shift mask comprises a transparent substrate (1) provided with a mask pattern formed by a light transmitting portion (4) for transmitting effective light beams having an intensity which substantially contributes to exposure and a light translucent portion (2) for transmitting ineffective light beams having an intensity which does not substantially contribute to exposure. The light translucent portion (2) is for phase shifting the ineffective light beams transmitted therethrough to make the ineffective light beams be different in phase from the effective light beams transmitted through the light transmitting portion (4) that the effective and the ineffective light beams passing through an area in the vicinity of a boundary between the light transmitting portion (4) and the light translucent portion (2) cancel each other so as to assure an excellent contrast at the boundary. The light translucent portion (2) comprises a thin film made of a material containing oxygen, metal, and silicon as main components.

This is a divisional of application Ser. No. 08/493,280 filed Jun. 21,1995 now U.S. Pat. No. 563,535.

BACKGROUND OF THE INVENTION

This invention relates to a phase shift mask capable of improving aresolution of a transfer pattern by imparting a phase difference toexposure light beams passing through the mask and to a phase shift maskblank from which the phase shift mask is made. More particularly, thisinvention relates to a phase shift mask of a so-called halftone type anda phase shift mask blank from which the phase shift mask is made.

To manufacture a semiconductor LSI, use is made of a phase shift maskwhich is known as one of photomasks for transferring a fine pattern. Thephase shift mask imparts a phase difference to exposure light beamspassing through the mask to thereby improve a resolution of a transferpattern. As one of those phase shift masks of the type described,Japanese Patent Publication (A) H04-136854 discloses a phase shift maskwhich is particularly adapted to transfer an isolated pattern such as asingle hole, dot, or line.

In the phase shift mask disclosed in the above-referenced publication, amask pattern formed on a transparent substrate comprises a lighttransmitting portion and a light translucent portion. The lighttransmitting portion transmits effective light beams having an intensitywhich substantially contributes to exposure. On the other hand, thelight translucent portion transmits ineffective light beams having anintensity which does not substantially contributes to exposure. Theineffective light beams passing through the light translucent portionare shifted in phase so that the ineffective light beams passing throughthe light translucent portion have a phase substantially reverse to thatof the effective light beams passing through the light transmittingportion. In this arrangement, the effective and the ineffective lightbeams passing through an area in the vicinity of a boundary between thelight transmitting portion and the light translucent portion cancel eachother. It is therefore possible to assure an excellent contrast at theboundary. The phase shift mask described above is called a halftonetype. In this phase shift mask, the light translucent portion has both alight shielding function of substantially shielding the effective lightbeams and a phase shift functiom of shifting the phase of theineffective light beams. Accordingly, it is unnecessary to separatelyform a light shielding film pattern and a phase shift film pattern.Thus, the phase shift mask is simple in structure and easy inmanufacture.

In the meanwhile, the light translucent portion in the above-mentionedphase shift mask of a halftone type is required to have optimum valuesfor both a light transmissivity and phase shift ability. If the lighttranslucent portion is formed by a single material, both of theabove-mentioned requirements must simultaneously be fulfilled byselecting its thickness. However, an appropriate material fullysatisfying such requirements has not yet been developed so far.

In view of the above, a proposal is made of an improved lighttranslucent portion of a multilayer structure comprising a plurality ofkinds of materials in the form of a high-transmissivity layer and alow-transmissivity layer. The low-transmissivity layer mainly serves toadjust the light transmissivity to a predetermined value. On the otherhand, the high-transmissivity layer mainly serves to adjust an amount ofthe phase shift. With this structure, it is readily possible to adjustboth the light transmissivity and the phase shift amount to optimumvalues. FIGS. 1 and 2 show phase shift masks each of which has a lighttranslucent portion of a multilayer structure. Referring to FIG. 1, thephase shift mask comprises a transparent substrate 10, a stopper film 11formed on the transparent substrate 10, a SOG (spin on glass) film 12formed on the stopper film 11 to serve as the high-transmissivity layer,and a chromium film 13 formed on the SOG film 12 to serve as thelow-transmissivity layer. Referring to FIG. 2, the phase shift maskcomprises the transparent substrate 10, the chromium film 13 formed onthe transparent substrate 10, and the SOG film 12 formed on the chromiumfilm 13.

However, the above-described phase shift masks with the lighttranslucent portions of a multilayer structure have followingdisadvantages.

As described above, the high-transmissivity layer and thelow-transmissivity layer are made of SOG and chromium, respectively.Therefore, when etching is carried out to form a mask pattern, it isrequired to use different kinds of etching media for the SOG film 12 andthe chromium film 13 as the high-transmissivity layer and thelow-transmissivity layer, respectively. It is assumed that both the SOGfilm 12 and the chromium film 13 are subjected to dry etching in orderto suppress occurrence of side etch. In this event, the SOG film 12 asthe high-transmissivity layer is etched by the use of a series offluoride etching gases such as CF₄, CHF₃, SF₆, C₂ F₆, NF₃, CF₄ +H₂,CBrF₃. On the other hand, the chromium film 13 as the low-transmissivitylayer is etched by a series of chlorine gases such as CCl₄ and C1₂. Ifboth of the films are successively etched in a same etching apparatus,one etching gas used earlier may remain in the apparatus to be mixedwith the other etching gas used later. This possibly results indisturbance of etching conditions. In order to eliminate the possibilityof such disturbance, it is proposed to etch those films in separateetching apparatuses. In this event, however, an additional etchingapparatus is required and the substrate must be moved from one etchingapparatus to the other. Furthermore, during the movement, foreignparticles such as dust may be attracted onto the substrate to cause adefective pattern to be formed. In addition, the SOG film has a lowrefractive index and must therefore be relatively thick. This means thatthe mask pattern has a large step height. As a result, the mask patternis readily damaged during washing and washability is insufficient toremove the foreign particles attracted thereto.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a phase shiftmask which is manufactured in a relatively simple process withoccurrence of a very small defect minimized and which is capable oftransferring a pattern with a high resolution.

It is another object of this invention to provide a method ofmanufacturing a phase shift mask blank from which a phase shift mask ofthe type described is made.

Other objects of this invention will become clear as the descriptionproceeds.

A phase shift mask to which this invention is applicable is for use inexposing a pattern and comprises a transparent substrate provided with amask pattern formed by a light transmitting portion for transmittingeffective light beams having an intensity which substantiallycontributes to exposure and a light translucent portion for transmittingineffective light beams having an intensity which does not substantiallycontribute to exposure. The light translucent portion is for phaseshifting the ineffective light beams transmitted therethrough to makethe ineffective light beams be different in phase from the effectivelight beams transmitted through the light transmitting portion so thatthe effective and the ineffective light beams passing through an area inthe vicinity of a boundary between the light transmitting portion andthe light translucent portion cancel each other so as to assure anexcellent contrast at the boundary.

According to this invention, the light translucent portion comprises athin film made of a material containing oxygen, metal, and silicon asmain components.

Preferably, the metal contained in the material of the thin film ismolybdenum.

Preferably, the thin film contains 35 to 60 at % oxygen.

Preferably, the material of the thin film contains nitrogen as anadditional component.

Preferably, the thin film contains nitrogen and oxygen in a ratiobetween 1:5 and 1:2.

Preferably, the thin film contains a variable content of oxygen varyingin a thickness direction so that the content is greater in the vicinityof a surface of the thin film than in a remaining part.

A phase shift mask blank to which this invention is applicable is foruse as a blank from which a phase shift mask of the type described ismade.

According to this invention, the phase shift mask blank comprises atransparent substrate and a thin film formed on the transparentsubstrate and made of a material containing oxygen, metal, and siliconas main components.

Preferably, the metal contained in the material of the thin film ismolybdenum.

As described above, the light translucent portion comprises the thinfilm made of the material containing oxygen, metal, and silicon as maincomponents. With this structure, although the light translucent portioncomprises a single-layer film made of a single material, it is readilypossible to simultaneously satisfy the requirements for the optimumvalues both in the light transmissivity and in the phase shift ability.The present inventors have found the fact that the thin film made of thematerial containing oxygen, metal (for example, molybdenum, tantalum, ortungsten), and silicon as main components is adapted to form the lighttranslucent portion. The light translucent portion comprising thesingle-layer film can be manufactured in an extremely simple process.Since the thin film has a high refractive index, the film thickness isrendered extremely small so that the mask pattern has a reduced stepheight. Accordingly, the mask pattern is prevented from being damagedduring washing and the washability is improved to effectively removeforeign particles.

When the metal contained in the material of the thin film is molybdenum,the above-mentioned effects of this invention are most remarkable.

When the thin film contains 35 to 60 at % oxygen, it is possible toobtain the light translucent portion having an excellent characteristic.

When the material of the thin film contains nitrogen as an additionalcomponent, it is possible to improve an acid resistance of the thin filmforming the light translucent portion as well as to selectively etchwith a high precision in dry etching of the thin film. Accordingly, thephase shift mask is easily manufactured.

When the thin film forming the light translucent portion contains avariable content of oxygen, only a surface portion accessed by acid isformed by a material containing a greater content of nitrogen to be richin acid resistance but low in light transmissivity. On the other hand,an internal portion is formed by a different material containing agreater content of oxygen to be poor in acid resistance but high inlight transmissivity. Thus, the light transmitting portion assures theoptimum light transmissivity as required and still has a sufficient acidresistance.

The phase shift mask blank having the above-mentioned structure can beused as a blank from which the phase shift mask of the type described ismade.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partial sectional view of a conventional phase shift mask ofa double layer structure;

FIG. 2 is a partial sectional view of another conventional phase shiftmask of a double layer structure;

FIG. 3 is a partial sectional view of a phase shift mask according toone embodiment of this invention;

FIG. 4 is a partial sectional view of a phase shift mask blank accordingto one embodiment of this invention; and

FIG. 5 is a graph showing a result of analysis upon a composition of alight translucent film used in this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Description will now be made as regards this invention with reference tothe drawing.

FIGS. 3 and 4 show a phase shift mask and a phase shift mask blankaccording to an embodiment of this invention, respectively.

At first referring to FIG. 3, the phase shift mask comprises atransparent substrate 1, a light translucent portion 2 formed on thetransparent substrate 1, and a light transmitting portion 4.

The transparent substrate 1 is made of silica glass and has top andbottom principal surfaces subjected to mirror polishing. The transparentsubstrate 1 has a length of 5 inches, a width of 5 inches, and athickness of 0.09 inches.

The light translucent portion 2 comprises a thin film made of a material(for example, MoSiO) containing oxygen, molybdenum, and silicon as maincomponents or another material (for example, MoSiON) containing nitrogenas an additional component in addition to oxygen, molybdenum, andsilicon. In this embodiment, a marcury lamp is used as an exposure lightsource to emit as an exposure light beam an i-ray having a wavelength(λ) equal to 365 nm. The light translucent portion 2 has an oxygencontent (at %), a nitrogen content (at %), a thickness d (A), and alight transmissivity which are selected so that the light translucentportion 2 has a predetermined phase shift amount (φ) and a predeterminedlight shielding ability with respect to the exposure light beam.

In this case, the thickness d is given by:

    d=(φ/360)×{λ/(n-1)},                      (1)

where n represents a refractive index of the light translucent portion2.

In Equation (1), the phase shift amount (φ) is preferably equal to 180°.Practically, the phase shift amount (φ) within a range between 160° and200° is sufficient. Generally, the light transmissivity of the lighttranslucent portion 2 with respect to the exposure light beam ispreferably within a range between 2% and 20%, although it depends upon asensitivity of a resist used in forming a mask pattern. The lighttransmissivity of the light translucent portion 2 is adjusted byselecting the oxygen content or the oxygen and the nitrogen contents ofthe thin film forming the light translucent portion 2.

Various samples of the thin film forming the light translucent portion 2were prepared at various contents of oxygen and at various contents ofoxygen and nitrogen. Table 1 shows characteristics of the samples (Nos.1 through 9) thus prepared. An acid resistance test was carried out byimmersion in a hot dense sulfuric acid solution (H₂ SO₄) at atemperature of 120° C. for two hours. In Table 1, reference symbols ∘and Δ represent that no variation in acid resistance was observed andthat variation within an allowable range was observed, respectively.

                  TABLE 1                                                         ______________________________________                                        Sam- Oxygen   Nitrogen Transmis-                                                                              Acid  Sheet Re-                               ple  Content  Content  sivity of                                                                              Resis-                                                                              sistance                                No.  (at %)   (at %)   i-ray (%)                                                                              tance (KΩ/□)                 ______________________________________                                        1    40       0        6        ∘                                                                       20                                      2    45       0        10       ∘                                                                       20                                      3    50       0        15       Δ                                                                             70                                      4    40       18       3        ∘                                                                       30                                      5    45       20       7        ∘                                                                       50                                      6    50       22       10       ∘                                                                       70                                      7    55       17       15       Δ                                                                             100                                     8    60       13       18       Δ                                                                             200                                     9    surface 43                                                                             20       15       ∘                                                                       30                                           bottom 50                                                                              17                                                              ______________________________________                                    

In Samples Nos. 1 through 3, the light translucent portion 2 comprises athin film made of MoSiO. In Samples Nos. 4 through 9, the lighttranslucent portion 2 comprises a thin film made of MoSiON. In SampleNo. 9, the thin film has a variable oxygen content varied in a thicknessdirection. Specifically, the oxygen content is smaller in the vicinityof a surface of the thin film than in a remaining part.

Next referring to FIG. 4, description will proceed to a manufacturingprocess of the phase shift mask having the above-mentioned structure.

As illustrated in FIG. 4, a light translucent film 2a comprising thethin film made of MoSiO (Samples Nos. 1 through 3) or MoSiON (SamplesNos. 4 through 9) is formed on the surface of the transparent substrate1 to obtain a phase shift mask blank.

When the light translucent film 2a comprises the thin film made of MoSiOas in Samples Nos. 1 through 3, the light translucent film 2a is formedin the manner which will presently be described.

By the use of a composite target comprising molybdenum (Mo) and silicon(Si) in a mol ratio of 1:2, reactive sputtering is carried out in amixed gas atmosphere containing argon (Ar) between 90% and 80% andoxygen (O₂) between 10% and 20% and having a pressure of 1.5×10⁻³ Torr.As a result, the thin film having a thickness between 1400 Å and 2000 Åis deposited on the transparent substrate 1. In Sample No. 2, the thinfilm having a thickness of 2000 Åwas formed in the mixed gas atmospherecontaining 85% argon (Ar) and 15% oxygen (O₂). In this case, thethickness is selected so that the phase difference is equal to 180°.

On the other hand, when the light translucent film 2a comprises the thinfilm made of MoSiON as in Samples Nos. 4 through 9, the lighttranslucent film 2ais manufactured as follows.

By the use of a composite target comprising molybdenum (Mo) and silicon(Si) in a mol ratio of 1:2, reactive sputtering is carried out in amixed gas atmosphere containing argon (Ar) between 84% and 72% andnitrogen monoxide (N₂ O) between 16% and 28% and having a pressure of1.5×10⁻³ Torr. As a result, the thin film having a thickness between1400 Å and 2000 Å is deposited on the transparent substrate 1. In SampleNo. 4, the thin film having a thickness of 1400 Å was formed in themixed gas atmosphere containing 84% argon (Ar) and 16% nitrogen monoxide(N₂ O). In this case, NO or O₂ +N₂ may be used instead of nitrogenmonoxide (N₂ O). In Sample No. 9, a partial pressure of argon (Ar) wascontrolled to provide the variable oxygen content varied in thethickness direction. FIG. 5 shows a result of analysis upon acomposition of the light translucent film of Sample No. 9 as analyzed bythe Auger analyzer. In the figure, an ordinate and an abscissa representthe content (%) of each element and a sputtering time (minute),respectively. It is noted here that the sputtering time corresponds to aposition in the thickness direction.

Subsequently, a resist film is formed on the light translucent film 2aof the phase shift mask blank thus obtained. Then, the phase shift maskblank with the resist film is subjected to a known pattern formingprocess comprising a series of steps of exposing, developing, etching,washing, and so on. As a consequence, a part of the light translucentfilm 2a is removed to obtain the phase shift mask having a hole or dotpattern formed by the light transmitting portion 4 and the lighttranslucent portion 2. If the MoSiO film or the MoSiON film is etched bydry etching, a CF₄ +O₂ mixture is used as an etching gas.

Referring to FIG. 3, it is assumed that exposure light beams L0 areirradiated to the phase shift mask. In this event, the exposure lightbeams L0 are separated into first light beams L1 and second light beamsL2. The first light beams L1 pass through the light translucent portion2 to reach a transfer object not illustrated in the figure. The secondlight beams L2 pass through the light transmitting portion 4 to reachthe transfer object. In this case, the first light beams L1 passingthrough the light translucent portion 2 have a weak intensity which doesnot substantially contribute to exposure. On the other hand, the secondlight beams L2 passing through the light transmitting portion 4 have astrong intensity which substantially contributes to exposure. In thisarrangement, exposure of the pattern is carried out. During theexposure, those of the first and the second light beams which passthrough a boundary area between the light translucent portion 2 and thelight transmitting portion 4 leak into the other side due todiffraction. However, those of the first and the second light beamscancel each other because the first and the second light beams aregenerally reverse in phase to each other. As a result, the lightintensity on the transfer object is substantially equal to zero at asite corresponding to the boundary area. Accordingly, a boundary isextremely definitely delineated so as to improve a resolution.

According to the above-mentioned embodiment, the light translucentportion 2 comprises the thin film made of the material containingoxygen, molybdenum, and silicon as main components. With this structure,it is possible to simultaneously satisfy the requirements for theoptimum values both in the light transmissivity and in the phase shiftability although the light translucent portion 2 has a single layerstructure instead of a multilayer structure. Because of such a singlelayer structure, the manufacturing process is very simple. In addition,the thickness of the thin film can be rendered extremely small becausethe thin film has a high refractive index. Therefore, according to thisinvention, the mask pattern has a reduced step height as small as a halfor one third as compared with the conventional phase shift mask having adouble layer structure comprising the SOG film and the chromium film.With such a reduced step height, the mask pattern is prevented frombeing damaged during washing and washability is improved to effectivelyremove foreign particles. Furthermore, the thin film made of thematerial containing oxygen,, molybdenum, and silicon as main componentscan easily be formed not only by sputtering but also by other commondeposition techniques such as vapor deposition. The light transmissivityand the acid resistance can be controlled as desired by adjusting theoxygen content or the oxygen and the nitrogen contents. Still more, aprecision in selective etching is improved in dry etching. Thus, thelight translucent portion having a desired characteristic is relativelyeasily obtained.

Since a film stress of the thin film is small, it is possible tosuppress a distortion of the mask and to assure tight contact betweenthe thin film and the transparent substrate such as a quartz substrate.

As the metal component of the material forming the light translucentportion, tantalum or tungsten may be used instead of molybdenummentioned above.

In the foregoing embodiment, the mercury lamp is used as the exposurelight source to emit, as the exposure light beam, the i-ray having awavelength of 365 nm. It is noted here that use can be made of adifferent exposure light beam having a different wavelength, forexample, a g-ray (436 nm) or a KrF excimer laser beam (248 nm). In suchan event, the oxygen content, the nitrogen content, and the filmthickness are adjusted in correspondence to the refractive index and theabsorption index of the thin film with respect to the wavelength of eachexposure light beam.

As thus far been described, according to this invention, the lighttranslucent portion comprises the thin film made of the materialcontaining oxygen, molybdenum, and silicon as main components. With thisstructure, it is possible to simultaneously satisfy the requirements forthe optimum values both in the light transmissivity and in the phaseshift ability although the light translucent portion comprises asingle-layer film made of a single material. Because the lighttranslucent portion comprises such a single-layer film, themanufacturing process is very simple. In addition, the thickness of thethin film can be rendered extremely small because the thin film has ahigh refractive index. Therefore, according to this invention, the maskpattern has a reduced step height so that the mask pattern is preventedfrom being damaged during washing and washability is improved toeffectively remove foreign particles. In addition, the thin film of thelight translucent portion may include silicide composed of the siliconand the metal.

What is claimed is:
 1. A method of manufacturing a phase shift maskblank, comprising the steps of:preparing a substrate transparent to anexposure light beam and a target comprising a metal and silicon;sputtering the target within an atmosphere of a mixed gas comprisingargon gas and N₂ O gas, to deposit onto the transparent substrate, atranslucent phase shift film which comprises the metal, oxygen,nitrogen, and silicon.
 2. A method as claimed in claim 1, wherein saidmixed gas includes 84% to 72% of the argon and 16% to 28% of a selectedone of NO and N₂ O.
 3. A method as claimed in claim 1, wherein the mixedgas includes 84% to 72% of the argon and 16% to 28% of N₂ O.
 4. A methodas claimed in claim 1, where the sputtering step is carried out bycontrolling a pressure of the said mixed gas so that an amount of oxygenis decreased from a back surface of said phase shift layer to a frontsurface along a thickness direction.
 5. A method as claimed in claim 1,wherein said metal comprises molybdenum.
 6. A method as claimed in claim5, wherein the target includes molydenum and silicon in a mol ratio of1:2.
 7. A method as claimed in claim 1, wherein the sputtering step isreactive sputtering.
 8. A method as claimed in claim 1, wherein thesputtering step comprises the steps of:controlling a pressure of themixed gas so that the translucent phase shift film has a contentdistribution of the oxygen in a direction of a thickness such that thecontent of the oxygen becomes lower at a portion adjacent to a surfaceof the translucent phase shift film in comparison with a portion remotefrom the surface.
 9. A method as claimed in claim 8, wherein the metalcomprises molybdenum.
 10. A method as claimed in claim 8, wherein thesputtering step is carried out by the use of a reactive sputteringtechnique.
 11. A method as claimed in claim 10, wherein the targetincludes molybdenum and silicon at a rate of 1:2.
 12. A method ofmanufacturing a phase shift mask, comprising the steps of:preparing asubstrate transparent to an exposure light beam and a target includingmetal and silicon; locating the transparent substrate and the targetwithin an atmosphere of a mixed gas which comprises argon gas and N₂ O;sputtering the target within the atmosphere onto the transparentsubstrate to deposit a translucent phase shift film which includes themetal, oxygen, nitrogen, and the silicon; and selectively etching thetranslucent phase shift film by the use of a photolithography techniqueto obtain the phase shift mask.
 13. A method of manufacturing a phaseshift mask blank, comprising the steps of:preparing a substratetransparent to an exposure light beam and a target including metal andsilicon; locating the transparent substrate and the target within anatmosphere of a mixed gas which includes an oxygen gas and a nitrogengas; adjusting amounts of the oxygen and the nitrogen within the mixedgas so that a translucent phase shift film deposited has a ratio ofnitrogen to oxygen which falls within a range between 0.2 and 0.5; andsputtering the target within the mixed gas adjusted onto the transparentsubstrate to deposit said translucent phase shift film which includesthe metal, the oxygen, the nitrogen, and the silicon and which includesthe nitrogen and the oxygen at the above-mentioned ratio.
 14. A methodas claimed in claim 13, wherein the sputtering step comprises the stepsof:controlling a pressure of the mixed gas so that the translucent phaseshift film has a content distribution of the oxygen in a direction of athickness such that the content of the oxygen becomes lower at a portionadjacent to a surface of the translucent phase shift film in comparisonwith a portion remote from the surface.
 15. A method as claimed in claim13, wherein the metal comprises molybdenum.
 16. A method as claimed inclaim 13, wherein the sputtering step is carried out by the use of areactive sputtering technique.
 17. A method of manufacturing a phaseshift mask blank, comprising the steps of:preparing a substratetransparent to an exposure light beam and a target including metal andsilicon; locating the transparent substrate and the target within anatmosphere of a mixed gas which includes an oxygen gas and a nitrogengas; adjusting amounts of the oxygen and the nitrogen within the mixedgas so that a translucent phase shift film deposited includes 35 at % to60 at % of oxygen; and sputtering the target within the mixed gasadjusted onto the transparent substrate to deposit said translucentphase shift film which includes the metal, the oxygen, the nitrogen, andthe silicon and which includes 35 at % to 60 at % of the oxygen.
 18. Amethod as claimed in claim 17, wherein the sputtering step comprises thesteps of:controlling a pressure of the mixed gas so that the translucentphase shift film has a content distribution of the oxygen in a directionof a thickness such that the content of the oxygen becomes lower at aportion adjacent to a surface of the translucent phase shift film incomparison with a portion remote from the surface.
 19. A method asclaimed in claim 17, wherein the metal comprises molybdenum.
 20. Amethod as claimed in claim 17 wherein the sputtering step is carried outby the use of a reactive sputtering technique.
 21. A method ofmanufacturing a phase shift mask blank, comprising the stepsof:preparing a substrate transparent to an exposure light beam and atarget including metal and silicon, locating the transparent substrateand the target within an atmosphere of a mixed gas which includes anoxygen gas and a nitrogen gas; adjusting amounts of the oxygen and thenitrogen within the mixed gas so that a translucent phase shift filmdeposited has a sheet resistance between 20 and 200KΩ/□; and sputteringthe target within the mixed gas adjusted onto the transparent substrateto deposit said translucent phase shift film including the metal, theoxygen, the nitrogen, and the silicon and which has the above-mentionedsheet resistance.
 22. A method as claimed in claim 21, wherein thesputtering step comprises the steps of;controlling a pressure of themixed gas so that the translucent phase shift film has a contentdistribution of the oxygen in a direction of a thickness such that thecontent of the oxygen becomes lower at a portion adjacent to a surfaceof the translucent phase shift film in comparison with a portion remotefrom the surface.
 23. A method as claimed in claim 21, wherein the metalcomprises molybdenum.
 24. A method as claimed in claim 21, wherein thesputtering step is carried out by the use of a reactive sputteringtechnique.
 25. A method of manufacturing a phase shift mask, comprisingthe steps of:preparing a substrate transparent to an exposure light beamand a target including metal and silicon; locating the transparentsubstrate and the target within an atmosphere of a mixed gas whichincludes an argon gas and a selected one of NO and N₂ O; sputtering thetarget within the atmosphere onto the transparent substrate to deposit atranslucent phase shift film which includes the metal, oxygen, nitrogen,and the silicon; and selectively etching the translucent phase shiftfilm by the use of a photolithography technique to obtain the phaseshift mask.
 26. A method of manufacturing a phase shift mask, comprisingthe steps of:preparing a substrate transparent to an exposure light beamand a target including metal and silicon; locating the transparentsubstrate and the target within an atmosphere of a mixed gas whichincludes an oxygen gas and a nitrogen gas; adjusting amounts of theoxygen and the nitrogen within the mixed gas so that a translucent phaseshift film deposited includes 35 at % to 60 at % of oxygen; sputteringthe target within the mixed gas adjusted onto the transparent substrateto deposit said translucent phase shift film which includes the metal,the oxygen, the nitrogen and the silicon and which includes 35 at % to60 at % of the oxygen; and selectively etching the translucent phaseshift film by the use of a photolithography technique to obtain thephase shift mask.
 27. A method of manufacturing a phase shiftmanufacturing a phase shift mask, comprising the steps of:preparing asubstrate transparent to an exposure light beam and a target includingmetal and silicon; locating the transparent substrate and the targetwithin an atmosphere of a mixed gas which includes an oxygen gas and anitrogen gas; adjusting amounts of the oxygen and the nitrogen withinthe mixed gas so that a translucent phase shift film deposited has aratio of nitrogen to oxygen which falls within the range between 0.2 and0.5; sputtering the target within the mixed gas adjusted onto thetransparent substrate to deposit said translucent phase shift film whichincludes the metal, the oxygen, the nitrogen and the silicon and whichincludes the nitrogen and the oxygen at the above-mentioned ratio; andselectively etching the translucent phase shift film by the use of aphotolithography technique to obtain the phase shift mask.
 28. A methodof manufacturing a phase shift mask, comprising the steps of:preparing asubstrate transparent to an exposure light beam and a target includingmetal and silicon; locating the transparent substrate and the targetwithin an atmosphere of a mixed gas which includes an oxygen gas and anitrogen gas; adjusting amounts of the oxygen and the nitrogen withinthe mixed gas so that a translucent phase shift film deposited has asheet resistance between 20 and 200 KΩ/□; sputtering the target withinthe mixed gas adjusted onto the transparent substrate to deposit saidtranslucent phase shift film including the metal, the oxygen, thenitrogen, and the silicon and which has the above-mentioned sheetresistance; and selectively etching the translucent phase shift film bythe use of a photolithography technique to obtain the phase shift mask.